package testJDK.java.util.concurrent;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class Mutex implements Lock {

    private static class Sync extends AbstractQueuedSynchronizer{

//        是否处于占用状态
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

//        当状态为0的时候获取锁
        @Override
        protected boolean tryAcquire(int arg) {
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

//        释放锁，将状态设置为0
        @Override
        protected boolean tryRelease(int arg) {
            if(getState()==0)  throw new IllegalMonitorStateException();
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

//        返回一个Condition,每个condition都包含了一个condition队列
        Condition newCondition(){
            return new ConditionObject();
        }
    }

//    仅需要将操作代理到Sync上即可
    private final Sync sync = new Sync();

    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean isLocked(){
        return sync.isHeldExclusively();
    }

    public boolean hasQueueThreads(){
        return sync.hasQueuedThreads();
    }
}
